Multi-Spray Barometric Condensers

As stated, a barometric leg is achieved by way of a tail pipe to drain the water and condensate from the condenser to a hot well at grade. The condenser is normally elevated to a sufficient height to permit this liquid to gravity flow down without any mechanical assistance. The minimum required height of the barometric leg is, therefore, a function of the maximum barometric pressure at the plant site and the operating (vacuum) pressure inside the condenser. As an example, let’s assume the maximum barometric pressure at a plant is 30″ HgA and that the condenser is operating at 4″ HgA, then the minimum required height of the barometric leg is a liquid column equating to 26″ Hg. As 1″ of Hg equals 1.133 feet of water, a minimum barometric leg of 29.5 feet is required. Note that this is the ‘minimum’ barometric leg height. It’s normally recommended that a 34 foot barometric leg be provided which allows the system to pull a pure vacuum and still allows the water and condensate to drain freely. The tail pipe of the barometric leg should be vertical with no horizontal bends. There should be a minimum of gasketed joints or welds in the tail pipe to minimize leakage potential. It must be “sealed”, that is, the outlet of the tail pipe must be at least 6″ below the minimum level of the water in the hot well. Barometric legs, if improperly designed and installed, can result in reduced vacuum capability.

In the Multi-Spray Barometric Condenser, the non-condensables are drawn through an air suction chamber to a pre-cooler, where water delivered by a spray nozzle lowers the temperature of the air-vapor mixture and condenses practically all of the vapor. The remaining mixture delivered to the air pump is at a temperature close to that of the spray water which reduces to a minimum the amount of condensable vapors removed by the air pump.